1. Field
The following description relates to a system and method for transferring and replicating a service among devices in a media content service environment, and more particularly, to an apparatus and method for synchronizing playback time of a media being provided to multiple devices during service transfer and replication process.
2. Description of the Related Art
As Internet use has grown, more attention has been given to media transfer over the Internet and to multimedia services using web technologies. To satisfy such interest in media services, studies on hypertext transfer protocol (HTTP) streaming and its standardization have been actively conducted for recent years. Some standardization organizations have established and distributed standard documents regarding technologies on HTTP-based streaming services. There are a number of HTTP-based media transfer platforms in use.
Media streaming has increased its role in content delivery over the Internet, and becomes essential to various applications, such as distance learning, digital libraries, home shopping services, video-on-demand services, and the like. For media content streaming services, various protocols, such as HTTP, Real Time Streaming Protocol (RTSP)/Real-time Transfer Protocol (RTP), Real Time Message Protocol (RTMP), Multi-media Message Service (MMS), and the like, are used. HTTP streaming is one of the most popular methods for media content services over the Internet. In HTTP streaming, media data/file is divided into a number of small pieces and the small pieces of data are sequentially transmitted through port 80/8080 to a receiver. The HTTP streaming may support a variety of streaming media formats such as MP4, MPEG2-TS, H.264/AAC and the like, and codecs, and use HTTP to provide streaming services by means of Windows Media/Silver Light Streaming, Flash Video, QuickTime Streaming server, Real Media Streaming, etc. The HTTP streaming has recently drawn increasing attention due to its superior streaming capabilities. A conventional media protocol uses a UDP port number that is rarely used, and thus in some cases a service is not available in some firewalls and routers.
In contrast, HTTP-based media transfer uses port 80/8080 only, and thus no traffic is blocked by existing firewalls or routers. In addition, a media service means using HTTP can advantageously use an inexpensive standard HTTP server and HTTP cache without the need of use of a specialized proxy and caches. Recently, HTTP is used in most cases to send a request from a content delivery network (CDN), to retrieve a multimedia object that is stored in a cache, and to communicate with a policy server.
Currently, technology standardization for streaming services using HTTP is in progress by a number of standard development organizations. 3GPP established the standard specification TS 26.234 for adaptive HTTP streaming as an alternative to media transfer using an existing RTSP/RTP, which deals with Media Presentation Description (MPD), media segmentation format, an HTTP server, client behaviors, and the like.
Open IPTV Forum (OIPF) has established technology specification for adaptive HTTP streaming, which is refined based on the 3GPP HTTP streaming specification so that it can be applied to OIPF services and devices. Recently, ISO/IEC JTC1/SC29/WG11 (MPEG) groups are under process of developing a new standard for HTTP streaming. This standard specifies requirements for transmitting MPEG media using HTTP, and its applications, and contents of documents (MPEG-1, MPEG-2, MPEG-3, MPEG-4) including purpose of establishment.
Media transfer platforms based on HTTP have been developed and used by a number of different companies in an effort to provide users with adaptive services with good service quality. Microsoft has implemented Smooth Streaming that is based on web over which media content is delivered using standard HTTP. Smooth Streaming does not deliver a media by downloading all data, but instead, divides the content a series of small “chunks” and sequentially delivering the chucks to a user and has advantages that files are easily cached to an edge server which is closer to a user. Adobe HTTP dynamic streaming suggested by Adobe systems Inc. enables real-time video streaming of media having various transmission rate and on-demand services.
Adobe HTTP dynamic streaming fragments a media file into smaller pieces, so that a Flash player user is allowed to use the media file without a need of downloading the entire file. Apple HTTP live streaming by Apple Inc. enables audio or video that is made previously or in real time to be played back on iOS-based devices, such as an iPhone, or on desktop computers running Mac OS X, and supports various transmission rates of existing web servers for media delivery.
1. Technique for Service Transfer between Terminals by OIPF (Open IPTV Forum)
The OIPF standardization group published service and platform requirements for release 2 related to service moving between terminals in December 2008, and thereafter announced related standard in September 2010. OIPF defines abilities, namely, session continuity and session portability in relation to service moving between terminals. Session continuity is the ability to move, in real time, a given service or application from one IPTV terminal functionality (ITF) to another resulting in the continuation of an existing session, and service portability is the ability that a given service or application can be utilized on various types of ITF for real-time continuation of a session.
In regard to session continuity, 1) session continuity should be supported under the control of a user, 2) when there is a request to move a session to another ITF, continuous service experience to the user should be supported, and 3) a mechanism for an IPTV service provider should be supported to duplicate an existing service session on another ITF.
To ensure session continuity, session transfer and session replication are defined. Session transfer allows a user to transfer an ongoing unicast session from a terminal (an original device) where the content is currently being streamed to another terminal (a target device) where the user can resume watching the same content. After the successful transfer of the session, the original session is terminated. Session replication allows a user to replicate an ongoing session from one terminal (an original device) to another terminal (a target device). The original session continues to be maintained after the successful replication of the session. After the session replication, the original device and the target device have completely independent sessions.
There are two modes of operation for session transfer and session replication depending on which terminal that requests the session transfer and the session replication. The two modes are push mode and pull mode. In push mode, an end-user requests to push the current session from a terminal that the user is currently using to a target terminal. In pull mode, an end-user uses a target terminal to pull a session that the user desires to transfer or replicate or uses the target terminal to request the replication of the session. OIPF standard has taken into consideration session transfer between terminals existing on the same access, for example, session transfer between terminals having the same IPTV subscription.
2. IMS (IP Multimedia Subsystem)-Based Technique for Inter-UE Service Transfer of 3GPP
This technique relates mobility of media flows and control of a session between different user equipment (UE) under the same subscription, and focuses on inter-UE transfer scenarios for transferring/retrieval/addition/deletion of media flows in a collaborative session, establishment or continuation of a collaborative session while transferring control, and the like.
For inter-UE service session transfer, IMS standard defines two types of UE: a controller UE and a controllee UE. A controller UE has the control of media flows, and a controllee UE is subordinate to the controller UE for media flow control. In addition, a collaborative session is defined for the support of service session transfer.
All UEs in a collaborative session support functionalities of (1) discovering an inter-UE transfer target for inter-UE transfer, (2) initiating inter-UE transfer procedures based on user inputs, and (3) acting as a controller UE in the collaborative session.
The general rules for providing IMS service session continuity are as follows. Inter-UE transfer for service continuity allows a multimedia session to be split to two or more UEs that are part of a collaborative session. The UEs are under the control of the same IMS subscription and may be connected to IMS core network (CN) from a diverse set of access network. A service centralization and continuity application server (SCC AS) is used to connect the UEs to their remote peer devices. The SCC AS performs control and management of a collaborative session. The controllee UE controls its media flow using media control signaling. The media control enables the controllee UE to operate.
Service consistency and service continuity functions are established so as to enable set up and session transfers of multimedia session across multiple UEs. One UE provides collaborative session control and the media flow is established using the UE providing the collaborative session control and/or other UEs.
To provide IMS service continuity, functionalities of establishment and release of the collaborative session, transferring, addition, modification and deletion of media flows and transferring of collaborative session controls are required. In a current media content service environment, due to a communication delay time between different devices during service transfer and replication process, media playback time changes after the service is delivered to a target terminal.